The present invention relates to a dry etching method, and more particularly, to a dry etching method capable of etching an article to be etched at a high rate and in exact accordance with a mask pattern.
The improvements in etching rate, selectivity and anisotropy of dry etching are described in the Proc. Dry Process Symp., 1986, page 42, the Proc. Dry Process Symp., 1986, page 83 and the Proc. Dry Process Symp., 1984, page 121, respectively, and are further described in many other publications. A dry etching method capable of satisfying two of three requirements (a high etching rate, high selectivity and marked anisotropy) is disclosed in, for example, a Japanese Patent Application JP-A-60-158,627. Further, a low-temperature dry etching method has been proposed.
However, conventional dry etching methods cannot satisfy the above-mentioned three requirements at the same time, but satisfy only one or two of the requirements. For example, in a conventional method, the etching rate is as high as 0.5 .mu.m/min and a ratio of the length of side etching to the etching depth is less than 1/100, but a selection ratio (that is, a ratio of the etching rate for an article to be etched to that for a mask material) is less than 5. Accordingly, the mask may be etched off in the course of an etching operation. In order to solve this problem, it is required to form a mask of an etching resistant film, for example, an SiO.sub.2 film. In this case, a manufacturing process is very complicated. Further, in another conventional method, the etching rate for an article to be etched is greater than 0.5 .mu.m/min and a ratio of the etching rate for the article to be etched to that for a mask material is greater than 10, but the length of side etching increases. Accordingly, a pattern formed in the article to be etched deviates from a mask pattern by 0.1 to 0.2 .mu.m, and such a deviation makes a large scale integration circuit defective. In a further conventional method, a ratio of the length of side etching to the etching depth and a ratio of the etching rate for the article to be etched to that for a mask material are both high, but the etching rate for the article to be etched is as low as about 0.1 .mu.m/min. Accordingly, it takes a very long time, for example, to form a deep groove in a silicon substrate by dry etching.